QC Radiopharmaceutical Tests PDF

Radiation protection 1- keep minimal exposure. 2-Clean neat lab , free from unnecessary equipment. 3-Short clean finger nails with no broken skin. 4-No smoking or eating in isotope labs. 5-Wear monitoring equipment: pocket dosimeter. 6- Use pipette filling devices. 7-Radio-protective agents: chemic...

Radiation protection 1- keep minimal exposure. 2-Clean neat lab , free from unnecessary equipment. 3-Short clean finger nails with no broken skin. 4-No smoking or eating in isotope labs. 5-Wear monitoring equipment: pocket dosimeter. 6- Use pipette filling devices. 7-Radio-protective agents: chemical physical Use specific shielding material for storing Injection or digestion or moving the of sulfhydryl groups radioactive compounds. Large dose of non Wear protective radioactive clothing, gloves, face compound of similar masks. composition Enhancing excretion Principles of radiation protection: >  >   is the most damaging due to its great charge and mass. Heavier particles have shorter ranges more energy per unit path length more damage (Non- penetrating radiations).  and x rays no charge and no mass much longer range in matter (Penetrating radiations). Four factors governing radiation exposure: 1- Time (directly proportional). 2- Distance (inversely to the square distance). 3-Shielding High atomic number materials (z) absorb radiation  and  particles are short in length so the containers act themselves as shields.  radiations on the other hand are highly penetrating highly absorbing materials should be used for protection (Lead). Half –value layer (HVL) : the thickness of shielding material that reduces the exposure from the radiation source to the half. It depends on both the energy of radiation and the atomic number of the absorbing material. High energy radiation?? High Z material?? 4- Activity Radiation hazard with the intensity of the radioactive source.  Receiving and monitoring of radioactive packages: Monitored for radioactive contamination. 3hrs after delivery. Monitoring Survey for external Wipe test exposure Survey for external exposure: Made using GM survey meter. At the surface ( 150 µm should be rejected possibility of pulmonary arterial blockade 1.2. pH and ionic strength:  Stability  Ideal pH :7.4 (blood)  It can vary from 2-9??  The pH of a solution is accurately measured by a pH meter, whereas colorimetric evaluation with pH paper (litmus paper) is rather inaccurate.  Any deviation should be treated with caution and should be remedied.  Proper ionic strength, isotonicity and osmolarity in order to be suitable for human administration.  Correction of ionic strength: acid, alkali, electrolyte. 1.3.Radionuclidic purity:  The ratio, expressed as a percentage, of the radioactivity of the desired radionuclide to the total radioactivity of the source.  Radionuclidic purity is defined as the fraction of the total radioactivity in the form of the desired radionuclide present in a radiopharmaceutical  99Mo in 99mTc- labeled preparation, iodine isotopes in 131I-labeled preparations (i.e: impurity may be from same element as the desired nuclide or from different element).  Is determined by measuring the half-life and characteristic radiations emitted by individual radionuclides.  Impurities arise from extraneous nuclear reactions due to isotopic impurities in the target material or from fission of heavy elements in the reactor.  The presence of these extraneous radionuclides increase the undue radiation dose to the patient and may also degrade the scintigraphic images.  Remove by appropriate chemical methods. 1.4.Radiochemical purity:  The proportion of the total activity of a specific radionuclide in a specific chemical or biologic form  The fraction of the total radioactivity in the form of the desired chemical present in a radiopharmaceutical.  Due to decomposition, solvent action, temp., pH, light, oxidizing or reducing agents.  Free 99mTcO4- and hydrolyzed 99m Tc in 99m Tc-labeled complexes and 51Cr+3 in a solution of 51Cr-sodium chromate.  Poor quality images due to high background from the surrounding tissues and from blood, unnecessary radiation dose to the patient.  Stability of a compound is time-dependant on exposure to light, temp. ( the longer the exposure the higher the decomposition).  So they are assigned an expiry date  Approaches to improve chemical stability:  Na ascorbate, ascorbic acid and Na sulphate are often added to maintain stability.  Store in dark area.  Store in refrigerator.  Analytical methods to detect and determine chemical impurities:  Ppt.  TLC  Gel chromatography.  Electrophoresis  Ion exchange  Solvent extraction  HPLC  Distillation 1.4.1.Precipitation:  PPT of one radiochemical entity from another with an appropriate chemical reagent, the ppt is then separated by centrifugation.  51Cr+3 present in 51Cr-sodium chromate solution may be measured by ppt chromate as lead chromate and determining the supernatant radioactivity. 1.4.2.Paper and instant TLC:  Small aliquot of the radiopharmaceutical preparation is spotted on a paper (whatman paper strip) or instant thin-layer chromatography (ITLC) strip (glass fiber impregnated with silica gel (SG) or polysilicic acid (SA)  Dip in an appropriate solvent (methanol, acetone, methyl ethyl ketone, 0.9%NaCl and water) contained in a jar or chamber.  The spot should remain above the solvent.  Different components of the sample distribute themselves between the adsorbent (stationary layer) and the solvent (mobile phase) depending on their distribution coefficients.  Electrostatic forces of the stationary phase tend to retard various components , while the mobile phase carries them along (move at different speed).  This effect and varying solubilities of different components in a solvent cause the individual components to move at different speeds and to appear at different distances along the paper or ITLC strip.  Polarity of the solvent also affects the chromatographic separation of different components in a sample.  Paper or ITLC can be ascending or descending.  Whereas some chromatography takes hours for the complete procedure, ITLC is a relatively fast method that takes only a few minutes.  Each component has a Rf value “ ratio of the distance traveled by the component to the distance the solvent front has moved from the original point “  Established with known components and Rf values are used preliminary for identification of diff. component from a given sample.  When the solvent front moves to a desired distance, the strip is removed, dried, divided horizontally into several segments, and the radioactivity is measured in each segment.  Histograms are obtained by plotting the radioactivity of each segment versus the distance of the strip.  Or, the activity along the strip can be measured by a radiochromatographic scanner (attached with an automatic integrator device) plots the radioactivity versus the distance of the strip.  Radiochemical impurity is calculated as the ratio of the radioactivity undesirable component to the total activity applied at the origin.  Precautions:  Dry strip.  Avoid streaking of solvent at the edge of the strip.  Sample spot should be small  Avoid long air drying 1.4.3.Gel chromatography:  Sample is spotted at the top of Sephadex gel or Bio-Rad gel  Soak in an appropriate solvent then elute with the same solvent.  Separation depends on the molecular size of the separated species, the lager one are eluted faster.  Sequential fractions of the eluate are collected by means of an automated fraction collector and the radioactivity is measured in each fraction.  The radioactivity is plotted versus fraction number which gives the relative conc. of different molecular size components in a given sample.  The amount of component is expressed as the ratio of its radioactivity to the total radioactivity placed on the column.  Gel chromatography is useful in separating proteins of different molecular weights.  This method is equally important in detecting impurities in 99mTc radiopharmaceuticals 1.4.4.Paper or polyacrylamide Gel electrophoresis:  Sample is applied on a paper or polyacrylamide gel soaked in a suitable buffer and then applying an appropriate voltage across the paper or gel for a specified time.  The components move across the paper or gel according to their charge or ionic mobility.  After electrophoresis, the distribution of activity along the strip or gel column can be determined by a counter or a radiochromatographic scanner.  Since protein molecules become charged in buffer solutions above or below their isoelectric pH, most proteins can be separated by this method with the use of appropriate buffers.  For example, a good separation of free iodide and radioiodinated proteins can be achieved by electrophoresis in buffer. 1.4.5.Ion exchange:  Resins: polymerized , high molecular weight, insoluble electrolytes.  2 components:  Large, heavy polymeric ion  Oppositely charged small ion that is exchangeable.  Radiopharmaceutical sample is passed through a column of ionic resin that is then eluted with a suitable solvent.  Separation of different species in a sample is achieved by the exchange of ions from the solution onto the resin depending on their relative affinity for this exchange under certain physicochemical conditions.  2 types:  Cation exchange resin:  R-H +Na+ R-Na + H+  caroboxylates, silicates, sulphonate groups  Dowex-50  Anion exchange resin:  R-OH + Cl- R-Cl + OH-  Quaternary amm. Compounds  Dowex-1  Pore size and cross-linkage of the resin affect the ion-exchange separation of different components in a sample.  An example of application of the ion-exchange method is the removal of unreacted iodide from an iodination mixture. Iodide is retained by the anion-exchange resin, whereas iodinated protein is eluted with the solvent. 1.4.6.Solvent extraction:  A solution containing one or more chemical compounds is shaken with an immiscible liquid.  Separation is affected by the preferential solubility of individual components in one solvent.  Partition coefficient: the ratio of solubility's of a component in two immiscible liquids.  Solvent extraction of 99m TcO4- with MEK (methyl ethyl ketone) from 99MoO4-2 has been a successful method of avoiding various radiocontaminants in the 99mTc-eluate.. 1.4.7.High-performance liquid chromatography (HPLC):  Separation of components with resolution.  Adv:  High resolution (separation of solutes of similar properties)  Speed  High recovery of solutes (separation of solutes even if present in minute quantities)  Columns  heavy-walled tubes of glass or stainless steel.  2-5 mm in diameter.  15-30 cm in length  Packed with appropriate packing material.  Packing material is very fine micro particulate  Operation:  Sample size is very small (5-250 µl)???  Sample is injected.  Eluent is then pumped into the column under pressure (6000 psi) at a controlled rate.  Eluate is passed into a sensitive detector that monitors the concentration of different solutes present.  The detector response is plotted against time after injection of the sample (retention time).  2 types:  Normal phase:  packing material is polar in nature, reacting OH groups of silica surface with various reagents.  Non polar solvents as hexane, heptane , acetone.  For samples of moderate to strong polarity.  Reverse phase:  packing material is non polar in nature, silica chemically bound to alkyl chains.  Polar solvents: water  For samples that are non polar to weakly polar.  Detectors:  To measure the conc. in the eluate.  UV or radiation detector.  Carbohydrates, drugs , proteins and fatty acids. 1.4.8.Distillation:  Two compounds with considerably different vapor pressure can be separated by simple distillation at a specific temperature  Higher vapor pressure (lower BP) will be distilled off first, leaving the other component in the distillation flask.  Iodide (present as a contaminant in an iodination mixture ) can be oxidized to iodine then separated by distillation.  Nobel gases (Xenon (133Xe), Krypton (81Kr) 1.5.Chemical purity:  The fraction of the material in the desired chemical form whether it is labeled or not.  Arise from the breakdown of the material either before or after labeling.  Al is a chemical impurity in the 99m Tc-eluate.  Globulins in the preparation of albumin.  The presence of chemical impurity before radiolabeling may result in  undesirable labeled compounds that may interfere with the diagnostic test.  Toxic effects  Purification by PPT, solvent extraction, ion exchange or distillation. 1.6.Radioassay:  The amount of radioactivity before dispensing as well as that of each individual dosage before administration.  Isotope dose calibrator.  The performance of the dose calibrator must be checked by carrying out the following quality control tests at the frequencies indicated:  Constancy (daily)  Accuracy (installation, annually, after repair)  Linearity (installation, quarterly, after repair)  Geometry (installation, after repair)  1.6.1.Constancy:  The constancy test indicates the reproducibility of measurements by a dose calibrator.  A deviation of the reading by more than ±10% may indicate the malfunction of the dose calibrator.  If above …..repair. 1.6.2.Accuracy:  Measuring the activities of at least two long-lived reference sources and comparing the measured activity with the stated activity.  The measured activity must agree with the stated activity within ±10%. 1.6.3.Linearity:  The ability of the dose calibrator to measure the activity accurately over a wide range of values.  200mCi to 2 Ci.  Start with the highest dose.  2 methods for checking the linearity:  Decay method  Shielding method 1.6.3.1.decay method:  A source of 99m Tc, with activity at least equal to the highest dosage normally administered to the patients in a given institute.  Assay the source at 0 hr and then every 6 hr during the working hours every day until the activity decays down to 30 µCi.  The measured activities are plotted against time interval on a semilog paper and the best fit straight line is drawn.  The deviation of the point farthest from the line is calculated.  If this deviation is more than ±10%, the dose calibrator needs to be replaced or adjusted, or correction factors must be applied. 1.6.3.2.Shielding method:  Less time consuming and easy to perform  Commercial calibration kit is used.  Seven concentric cylindrical tubes or “sleeves”.  The innermost tube is not lead-lined ….no attenuation of gamma radiations.  The other six tubes are lead-lined with increasing thickness to simulate the various periods of decay.  When these tubes are placed over the source of a radionuclide (normally 99mTc) in the dose calibrator, seven activity measurements represent activities at different times. 1.6.4.Geometry:  Variations in sample volumes or geometric configurations of the container can affect the accuracy of measurements in a dose calibrator.  Thus, same activity in different volumes or in different containers may give different readings in the dose calibrator.  If the difference exceeds ±10%, correction factors must be established for changes in volume or container configuration. 3 mCi 2. Biological Tests 2.1. Sterility Sterility indicates the absence of any viable bacteria or microorganisms in a radiopharmaceutical preparation. Methods of Sterilization 2.1.1. Dry heat sterilization:  Carried out at 180° for 2 hours or 260° for 45 minutes in a hot air oven.  Used for thermostable oily solutions.  Dry heat is not suitable for short-lived radionuclides such as 13N and 18F.  Dry heat cause coagulation of protein of m.o. 2.1.2.Moist heat sterilization (autoclaving):  In autoclaving, the radiopharmaceutical is sterilized by heating in steam under pressure at 115°C for 30 min., 121°C for 15 min. or 132°C for 3 min. in an autoclave.  Autoclaving is suitable only for thermostable aqueous solutions. Autoclaving is also not suitable for short-lived radionuclides.  Moist heat causes coagulation of proteins of m.o.  Moist heat sterilization is more effective than dry heat sterilization since steam has more penetration power, heating capacity and coagulating effect than hot air. 2.1.3. Gas sterilization:  Used for sterilization of thermolabile radiopharmaceuticals in the dry powder state (because drugs in the liquid state may undergo alkylation).  SO2 & formaldehyde were used but they are highly reactive & irritant.  Now, ethylene oxide and β-propiolactone are used.  Ethylene oxide is highly flammable, so it is mixed with an inert gas e.g. N2, CO2 or Freon.  Ethylene oxide exerts its lethal effect on m.o. by alkylating its essential metabolites. 2.1.4. Ionizing radiation:  Carried out by -radiation or electron beam radiation.  Dose of -radiation is 2.5 megarads.  Used for sterilization of thermolabile radiopharmaceuticals.  Ionizing radiation cause ionization and damage of the cells of the m.o. leading to its death 2.1.5. Membrane filtration:  Membrane filtration consists of simply filtering the radiopharmaceutical through a membrane filter that removes various organisms by one of three mechanisms: sieving, adsorption, or electrostatic attraction.  Membrane filtration is the method of choice for short-lived and heat-labile radiopharmaceuticals such as blood products.  The most common membrane filter pore size is 0.45 µm, but a smaller pore size of 0.22 µm is necessary for the sterilization of blood products and preparations suspected of contamination with smaller microorganisms. Testing of filters: 1. Bubble point test: The filter is wetted with water; air pressure is applied to the surface and gradually increased till bubbles appear. The pressure at this point is called bubble point pressure which is inversely proportional to the pore size. If there is any leakage in the filter, bubbling will occur at a lower pressure. A 0.22 µ pore size has a bubble point pressure of 55 psig. ↓↓↓↓↓↓↓ ---------------------- 2. Microbial challenge test: A culture containing a large number of small microorganisms e.g. P. diminuta is filtered through the filter. A sterility test is carried out on the filtrate. Presence of bacteria indicates defect in the filter. Sterility Testing 1. Official method (in USP):  The sterility test in this method is performed by incubating the radiopharmaceutical sample in fluid thioglycollate medium (for anaerobic microorganisms) at 30 to 350C for 14 days.  Another test uses soybean medium (for aerobic microorganisms) for incubation at 20 to 250C for 14 days.  If bacterial growth, as indicated by turbidity, is observed in either test, the radiopharmaceutical is considered to be non-sterile.  This method is not suitable for short-lived radionuclides such as 99mTc, since it takes a long time. 2. Non-official method:  The sterility test in this method depends on the metabolism of 14C-glucose by microorganisms present in the material under test.  The test involves the addition of the test sample to a culture medium containing 14C-glucose, then incubation, and finally collection and radioassay of 14CO2 formed by the metabolism of glucose by microorganisms, if present, in the sample.  Both aerobic and anaerobic microorganisms can be detected by this method.  This method is suitable for short-lived radionuclides such as 99mTc, because it requires only a short time, about 3 to 24 hr, compared to the 14 days in the previous method. 2.2. Apyrogenicity:  All radiopharmaceuticals for human administration are required to be pyrogen free.  Pyrogens are the metabolic products of microorganisms. They are phospholipids. The most dangerous pyrogens are those produced by Gm –ve bacilli.  Pyrogens cause fever and may lead to death in large doses.  They are 0.05 to 1 μm in size, and in general, are soluble and heat stable. They can be destroyed by heating at 175º for 3 hours.  Other less effective techniques for pyrogen removal include filtration, adsorption or chemical oxidation.  Sterility of a solution does not guarantee its apyrogenicity nor does sterilization destroy pyrogens in a radiopharmaceutical.  Since pyrogens arise mainly from the metabolism of bacteria, the best way to prevent pyrogenic contamination is to use sterile glassware, solutions, and equipment under aseptic conditions in any preparation procedure. Pyrogen Testing 2.2.1. Rabbit method: (official in USP):  Three healthy rabbits of weight 2-2.5 Kg and temp. not exceeding 39.8ºC and temp. change not more than 1ºC from each other, are used.  Inject 1 ml of the test solution/kg body weight in an ear vein of each rabbit.  The test solution is warmed to 37ºC before injection.  Record the rectal temp for each rabbit at 1, 2 & 3 hr after injection. The solution is accepted if:  Temp rise in each rabbit is not more than 0.6ºC, or  The total temp. rise in the 3 rabbits is not more than 1.4ºC. If the temp. rise exceeds these limits, repeat the test using another 5 rabbits and the sample will be accepted if:  Temp rise in each rabbit is not more than 0.6ºC, or  The total temp. rise in the 8 rabbits is not more than 3.7º 2.2.2. Limulus test (non-official):  The test solution is added to the blood lysate of the horse shoe crab (Limulus polyphemus) and if pyrogen is present, a gel will be formed within 15 to 60 min.  This test is also called LAL test (Limulus Amebocyte Lysate).  Precautions of this test: 1. Alcoholic solvents cause precipitation of the lysate and therefore must be avoided. 2. Several proteins at high concentrations tend to produce gel even without pyrogen and should be diluted to appropriate concentrations before the test.  Advantages of this test: more sensitive, more rapid & easier to perform. 3. Toxicity:  Before any radiopharmaceutical is approved for human use, its toxic effect and safe dosage must be established.  Toxic effects due to radiopharmaceutical administration include alterations in the histology or physiologic functions of different organs in the body or even death.  Tests for acute or chronic toxicity can be carried out in various animals such as mice, rats, rabbits and dogs.  A quantity, called the LD50/60, describes the toxic effect of a radiopharmaceutical. It is the dosage required to produce 50% mortality in 60 days in any species after administration of the radiopharmaceutical. For determination of the LD50/60, the test substance is injected in increasing dosages into a large group of animals. The dosage at which 50% mortality of the animals is observed in 60 days following administration is established as the LD50/60 for the material. From these studies, a safety dosage is established for human use. In most radiopharmaceuticals, toxicity arises from the pharmaceutical part of the radiopharmaceutical, not from the radionuclide part. Nuclear pharmacy: Actually, there is no difference between the two terms nuclear pharmacy and radiopharmacy and they can be used interchangeably. The nuclear pharmacy is staffed with trained personnel such as radiopharmacists and radiochemists. Role of the nuclear pharmacy 1. In a nuclear pharmacy, radiopharmaceuticals are prepared, stored, and dispensed primarily for human use, just as regular drugs are in a pharmacy. 2. The nuclear pharmacy may serve as a center for education and training of pharmacy and nuclear medicine students. 3. The nuclear pharmacy engages in basic research in the design and development of new radiopharmaceuticals. 4. In the nuclear pharmacy, the remedy for any adverse reaction in humans due to the administration of radiopharmaceuticals is found. Design of a Nuclear Pharmacy: Several common problems should be kept in mind when designing a nuclear pharmacy unit: 1. Protection of personnel from radiation hazard, 2. Avoidance of contamination of work area, 3. Radiation-detection instruments, 4. Clean air circulation in the dispensing area 5. Disposal of radioactive waste. *A nuclear pharmacy should be located within or near the nuclear medicine department because there is a close relationship between the two units. *The nuclear pharmacy area can be as small as a 12 ft x 12 ft (4 m x 4 m) room for small operation. For a larger operation, the unit may consist of several rooms. *It should have enough space for accommodating offices, a counting room, and a health physics laboratory on one side of a corridor, and a high radiation laboratory (hot lab), a compounding room, a storeroom, and a dispensing area on the other side. *******Design of a Nuclear Pharmacy****** ------------------------------------------------------------------------------------------- OFFICES || COUNTING ROOM || HEALTH PHYSICS LAB. --------- ------------------------ ---------------------------------- ------------------- CORRIDOR ------------------ ---------------------------------- ------------------------ ------------- Dispensing Area || Compounding Room || Store Room II Hot Lab. ---------------------------------------------------------------------------------------------- Various pieces of equipment are essential for good operation of nuclear pharmacy. Examples are: (1) a dose calibrator capable of measuring various types and levels of radioactivity, (2) chromatography equipment, (3) radiation survey meters, (4) an area monitor, (5) a pH meter, (6) a light microscope for particle size determination, (7) a detector to identify contaminants in radiopharmaceuticals, (8) lead-lined refrigerators and freezers to store cold kits and radiopharmaceuticals under refrigeration, (9) a hot water-bath, and (10) a dry heat oven. Operation of a Nuclear Pharmacy The daily operation of a nuclear pharmacy involves the following steps: (1) receiving of radioactive materials, (2) preparation of radiopharmaceuticals, (3) quality control tests of radiopharmaceuticals, (4) storage, (5) dispensing, (6) radioactive waste disposal, and (7) infectious waste disposal. Centralized Nuclear Pharmacy It is rather expensive to operate a separate nuclear pharmacy within a small nuclear medicine department. A centralized nuclear pharmacy in any region having reasonable transportation facilities can lead to significant savings of money and time. It must be shared by many, if not all, hospitals in a given region; otherwise it may not be feasible (suitable) to run it economically. A centralized nuclear pharmacy would have the following advantages: 1. save time 2. save workers 3. there is also less possibility of radioactive contamination.